Development of Nervous System

Question 1

Describe the process of neuralation

Answer 1

1) notochord induction forming neural plate
2) neural plate deepens to form neural groove
3) groove folds together in midline and break free to form neural tube
4) neural tube goes to form brain and spinal cord

Question 2

What does the centre hollow space of neural tube become?

Answer 2

the ventricular system

Question 3

Neural tube is initially ________ thick with a ______ centre. There is a rostral to caudal gradient of formation, and ______ is older

Answer 3

one cell
hollow
rostral end

Question 4

Describe the order of neural fold closure as they are independent events

Answer 4

closure goes in the order of

1) mid back
2) head to just above top of the neck
3) front of forehead
4) back of the head, between step 1 + 2
5) tail end

Question 5

Failure of closing the tail end = ?

Is it common? what are the possible consequences?

Answer 5

spina bifida
yes, it is the most common defect of neural fold closure
get a blister of open neural tube + movement deficit in the lower limbs

Question 6

What is the most severe form of neural fold defect?

Answer 6

anencephaly - still born baby lacking higher brain centre

Question 7

What are the three initial swellings of neural tube in the rostral end? How many cell layers are in each swelling?

Answer 7

Prosencephalon, mesencephalon, rhombencephalon

1 cell thick still

Question 8

What are the two distinct fissures during tube segmentation?

Answer 8

cephalic and cervical flexures

Question 9

What does prosencephalon split into?

Answer 9

telencephalon and diencephalon

Question 10

List the PNS neural crest derivatives

Answer 10

DRG, SNS/PNS/ENS ganglia, Schwann cells

Question 11

How are optic vesicles formed? What do they become? What is the significance of it?

Answer 11

outpockets of diencephalon, and go on to become the retina. Retina injury has CNS pattern

Question 12

What do neural crest cells give rise to apart from PNS structures?

Answer 12

melanocytes, muscle/cartilage bones of the face, dentine

Question 13

T/F developing cells are very mobile

Answer 13

True, neural crest cells can migrate a fair distance

Question 14

Enteric neural crest migration begins at the _______ all the way to _______ . it is the _______ network of migration. The same migrating pattern can be seen in ______ cells

Answer 14

oesophagus
anus
largest
cancer

Question 15

What type of cell is the neuroepithelium of neural tube?

Answer 15

columnar

Question 16

Describe the process of adding layers to generate cortex

Answer 16

proliferation of cells occur in the ventricular zone and daughter cells migrate to outer surface via radial glial cells.

The process is “inside-out” - adding cells on the inside, but cells migrate to the outside

Question 17

What is a stem cell

Answer 17

cells that can self renew indefinitely and remain undifferentiated

Question 18

Which genes can mutate and result in smooth, unfolded brain surface and mental retardation?

Answer 18

Reelin and DCX

Question 19

What is the most common cause of male autism?

Answer 19

Fragile X syndrome, affecting the connectivity of brain

Question 20

T/F neurons controlling distal muscles are more medial in the spinal cord

Answer 20

False, the organisation follows topographic organisation such that neurons for limbs are located laterally

Question 21

T/F Motor neurons are ventral to sensory neurons

Answer 21

True, “dorsal” root ganglion houses sensory neuron cell bodies, and they are located dorsally

Question 22

In spinal cord development, the notochord releases _______ to induces the formation of _________ , which will in turn use the same molecule to induce formation of _______ in the _______ horn

Answer 22

sonic hedgehog
floor plate
motor neurons
ventral

Question 23

how do interneurons form?

Answer 23

motor neurons release motor-neuron factor to induce formation of interneurons

Question 24

Describe the first step of axonal growth

Answer 24

when the embryo is still small, pioneer axons lay down the initial scaffold of axon tracts for later axons to navigate

Question 25

What is a growth cone

Answer 25

the tip of axon and the site of axon extension.

Cell body just adds material for axons to extend

Question 26

How do axons know where to go?

Answer 26

they follow gradients of chemical in the embryo, which can either attract or repel them

Question 27

What is the critical period

Answer 27

refinement of the imperfect, infant nervous system, leading to permanent changes that establish mature functional nervous system.

Can occur postnatally

Question 28

T/F visual input from left and right eyes are segregated

Answer 28

True, and this can be seen in visual cortex where there are alternating bands

Question 29

What happens if we sew shut a cat’s eye during the critical period?

Answer 29

the sewed eye is likely to become permanently blind, and it’s not because the retina is not working, but because the visual cortex is not responding

Question 30

What is the principle of plasticity in critical period

Answer 30

use it or lose it, and it’s the relative activity that’s important
repetitive stimulus is potentiated
unused information is depressed